This invention relates in general to mining machines and in particular to a new and useful device for extending flexible power supply lines to a mining machine on a conveyor structure.
In longwall operations, mining machines are moved back and forth the entire length of a longwall face and, as a rule, are guided on a conveyor structure. The mining machine is moved either by a traction chain or rope which is driven from the end of the longwall, or by a drive mechanism forming part of the mining machine. Various arrangements are known for supplying the mining machine with means for driving and operating, which will be termed "power" for short in the following.
For example, power supply lines may extend in a cable channel and be towed along by the mining machine, with the cable channel being mounted on a conveyor structure. With such an arrangement, it is usual to lay the lines individually, or bundled in a cable chain. It is further known to train the power lines as loops by means of a cable trolley which is guided in a side bracket channel of the conveyor and equipped with guide rollers for the lines. The cable trolley is moved by the mining machine or, in accordance with the travel thereof, by winches from the working face ends.
With low traveling speeds of the mining machine, the first named method may still be satisfactory for a regular laying of the towed lines. With higher speeds, however, this becomes problematic. The relatively high friction resistance encountered by the towed lines on the stationary surface strongly shortens the life of the lines. Frequent bending beyond the minimum radius, primarily in low seams, increases the risk of fatigue failures in the lines. The use of cable chains produces considerable additional noise in operation. Further, dislodged material, accumulating in the cable channel which is open at its top, hinders the cable guidance. In addition to the drawbacks connected to the cable chain guidance, a guidance in loops entails jerky loads leading to strong local whips toward the sides and/or vertically of the line portions. This requires sufficiently high brackets for the cable channel, preventing the structure from being used in lower workings.
Further known is a power supply arrangement providing that the mining machine pulled back and forth along the face is guided on a conveyor structure, and the supply lines are gathered and stored at the longwall ends and continuously laid down onto the element pulling the machine, within a housing which is secured to the conveyor structure. The element pulling the machine carries supporting strips for receiving the supply lines placed thereon. The supporting strips may be forked. The channel for receiving the power supply lines which extend stretched along the face is open upwardly and may become filled with the extracted material. This material, the bulk of which is taken along by the flights of the conveyor chain, appreciably increases the frictional resistance. Fragments from the roof may fall down into the open channel and damage the lines or the supporting strips. Also, in this arrangement, the power line and the traction element are strained unequally, so that the supporting strips and the lines are in perpetual motion relative to each other, which augments the wear and additionally stresses the lines. The introduction of the flexible supply lines at the end of the longwall becomes expensive and problematic, particularly in view of the "hanging chain" which is expected and its soiling.